The Effectiveness of Local Antibiotics in Treating Chronic Osteomyelitis in a Cohort of 50 Patients with an Average of 4 Years Follow-Up

Antibiotics Limit Adaptation of Drug-Resistant Staphylococcus aureus to Hypoxia

Bacterial pathogens are confronted with a range of challenges at the site of infection, including exposure to antibiotic treatment and harsh physiological conditions, that can alter the fitness benefits and costs of acquiring antibiotic resistance. Here, we develop an experimental system to recapitulate resistance gene acquisition by Staphylococcus aureus and test how the subsequent evolution of the resistant bacterium is modulated by antibiotic treatment and oxygen levels, both of which are known to vary extensively at sites of infection. We show that acquiring tetracycline resistance was costly, reducing competitive growth against the isogenic strain without the resistance gene in the absence of the antibiotic, for S. aureus under hypoxic but not normoxic conditions. Treatment with tetracycline or doxycycline drove the emergence of enhanced resistance through mutations in an RluD-like protein-encoding gene and duplications of tetL, encoding the acquired tetracycline-specific efflux pump. In contrast, evolutionary adaptation by S. aureus to hypoxic conditions, which evolved in the absence of antibiotics through mutations affecting gyrB, was impeded by antibiotic treatment. Together, these data suggest that the horizontal acquisition of a new resistance mechanism is merely a starting point for the emergence of high-level resistance under antibiotic selection but that antibiotic treatment constrains pathogen adaptation to other important environmental selective forces such as hypoxia, which in turn could limit the survival of these highly resistant but poorly adapted genotypes after antibiotic treatment is ended.

Collagen fleece in orthopaedic infections

Collagen fleece is a relatively new development. It represents another option in the battle against infection. It is a cheap, biocompatible, and resorbable local antibiotic delivery mechanism with favorable drug release kinetics and low risk of adverse effects or toxicity. Benefit may be conferred when used in contaminated cases. Significantly more research is still needed before the adoption of collagen fleece as the standard of care. However, we can likely conclude that there are no major adverse effects and it can be safely used as an adjunct in addition to conventional therapies for the prophylaxis and treatment of infections.

Antibiotic-Loaded Collagen Sponges in Clinical Treatment of Chronic Osteomyelitis: A Systematic Review

BACKGROUND

Chronic osteomyelitis is caused by bacterial infection of the bone and is a major problem in orthopaedic surgery. Treatment of chronic osteomyelitis requires surgical debridement accompanied by local and systemic administration of antibiotics. A widely established biodegradable local antibiotic carrier is antibiotic-loaded collagen sponges (fleeces). These sponges are commonly used in the treatment of chronic osteomyelitis, but a systematic review of their clinical efficacy and assessment of the quality of evidence have not been conducted, to our knowledge.

METHODS

This systematic review, performed according to the PRISMA statement, examined the clinical efficacy of and quality of evidence regarding different antibiotic-loaded collagen sponges in the clinical treatment of chronic osteomyelitis. Clinical efficacy was defined as eradication of infection with bone and wound-healing. In addition, the in vivo pharmacokinetics of the various collagen sponges were evaluated. Quality was based on the Level of Evidence, methodological quality, and risks of bias.

RESULTS

A total of 813 articles were screened, and 10 were included. Gentamicin-sulfate sponges and gentamicin-sulfate/gentamicin-crobefate sponges were studied. A total of 413 patients were treated, with a success rate of 91%. Reported complications were fistulas, prolonged wound drainage, and wound-healing problems. In vivo pharmacokinetic profiles showed an average local antibiotic concentration that was above the minimum inhibitory concentration for only 5 days. The general quality of the included studies was low to moderate, and there was a moderate to high risk of bias.

CONCLUSIONS

The evidence quality and Level of Evidence of the included studies were low, and the risk of bias in these studies was high. This makes the evidence regarding these sponges inconclusive, and no clinical decision-making can be based on these studies. Utilization of antibiotic-loaded collagen sponges in the treatment of chronic osteomyelitis should only be carried out with caution; studies with high-level evidence are needed.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Chronic Osteomyelitis - Bacterial Flora, Antibiotic Sensitivity and Treatment Challenges

Background:

Chronic osteomyelitis is a catastrophic sequel of delayed diagnosis of acute osteomyelitis.

Objectives:

The objectives of the study were to determine bacterial flora and antibiotic sensitivity, and to evaluate the outcome of an aggressive surgical approach to chronic osteomyelitis.

Methods:

This is a single surgeon, prospective cohort study on 30 consecutive patients with clinically and radiologically diagnosed chronic osteomyelitis presented to a hospital. We prospectively recorded demographic, clinical, radiological features, treatment protocol, microbiologic results of culture and sensitivity. The main treatment outcome measures were clinical signs of eradication of infection.

Results:

Microbiologic results showed that Gram-negative and mixed flora accounts for more than half of chronic osteomyelitis cases while Staphylococcus aureus was a dominating single pathogen (39%). We detected a high resistance rate to common antibiotics, e.g. 83% of S. aureus isolates were resistant to oxacillin (MRSA). The mean duration of bone infection was 4.2 years (3 months to 30 years) and the mean number of operations was 1.5 (1-5) . The mean follow-up was 15 months (12-18 months). Infection was eradicated in 95% (21 out of 22) treated by a single procedure and in all patients (n=8) by double procedure.

Conclusion:

Presented the high rate of MRSA strains is alarming and calls for updating of the antibiotic therapy guidelines in the country. Good results in treatment of chronic osteomyelitis can be achieved by a single-stage protocol including radical debridement combined with systemic and topical antibiotic.

The Classification of Long Bone Osteomyelitis: A Systemic Review of the Literature

Background: Osteomyelitis is a complex disease. Treatment involves a combination of bone resection, antimicrobials and soft-tissue coverage. There is a difficulty in unifying a classification system for long bone osteomyelitis that is generally accepted.

Objectives: In this systematic review, we aim to investigate the classification systems for long bone osteomyelitis that have been presented within the literature. By doing this, we hope to elucidate the important variables that are required when classifying osteomyelitis.

Methods: A complete search of the Medline, EMBASE, Cochrane and Ovid databases was undertaken. Following exclusion criteria, 13 classification systems for long-bone osteomyelitis were included for review.

Results: The 13 classification systems that were included for review presented seven different variables that were used for classification. Ten of them used only one main variable, two used two variables and one used seven variables. The variables included bone involvement (used in 7 classification systems), acute versus chronic infection (used in 6), aetiopathogenesis (used in 3), host status (used in 3), soft tissue (used in 2), microbiology (used in 1) and location of infected bone (used in 1). The purpose of each classification system could be grouped as either descriptive (3 classification systems), prognostic (4) or for management (4). Two of the 13 classification systems were for both prognostic and management purposes.

Conclusions: This systematic review has demonstrated a variety of variables used for classification of long bone osteomyelitis. While some variables are used to guide management and rehabilitation after surgery (e.g., bone defect, soft tissue coverage), others were postulated to provide prognostic information (e.g., host status). Finally, some variables were used for descriptive purposes only (aetiopathogenesis). In our view and from today's perspective, bone involvement, antimicrobial resistance patterns of causative micro-organisms, the need for soft-tissue coverage and host status are important variables to include in a classification system.

Current treatment of infected non-union after intramedullary nailing

Non-union is a devastating consequence of a fracture. Non-unions cause substantial patient morbidity with patients suffering from loss of function of the affected extremity, increased pain, and a substantial decrease in the quality of life. The management is often associated with repeated, unsuccessful operations resulting in prolonged hospital stays, which has social and economic consequences to both the patient and the healthcare system. The rates of non-union following intramedullary (IM) nailing vary according to anatomical location. There is currently no consensus regarding the treatment of infected non-unions following IM nailing, but the most common procedures reported are; exchange IM nail with antibiotic suppression or excision of the non-union, (stabilisation with external fixation or less commonly plate or IM nail) and then reconstruction of the bone defect with distraction osteogenesis or the Masquelet technique. This article explores the general principles of treatment, fixation modalities and proposes a treatment strategy for the management of infected non-unions following intramedullary nailing.

Role of Systemic and Local Antibiotics in the Treatment of Open Fractures

The orthopedic community has learned much about the treatment of open fractures from the tremendous work of Ramon Gustilo, Michael Patzakis, and others; however, open fractures continue to be very difficult challenges. Type III open fractures continue to be associated with high infection rates. Some combination of systemic and local antibiotics may be most appropriate in these high-grade open fractures. Further research is still necessary in determining optimal systemic antibiotic regimens as well as the role of local antibiotics. Any new discoveries related to novel systemic antibiotics or local antibiotic carriers will need to be evaluated related to cost.

Induced membrane technique for the treatment of bone defects due to post-traumatic osteomyelitis

Objectives

Induced membrane technique is a relatively new technique in the reconstruction of large bone defects. It involves the implantation of polymethylmethacrylate (PMMA) cement in the bone defects to induce the formation of membranes after radical debridement and reconstruction of bone defects using an autologous cancellous bone graft in a span of four to eight weeks. The purpose of this study was to explore the clinical outcomes of the induced membrane technique for the treatment of post-traumatic osteomyelitis in 32 patients.

Methods

A total of 32 cases of post-traumatic osteomyelitis were admitted to our department between August 2011 and October 2012. This retrospective study included 22 men and ten women, with a mean age of 40 years (19 to 70). Within this group there were 20 tibias and 12 femurs with a mean defect of 5 cm (1.5 to 12.5). Antibiotic-loaded PMMA cement was inserted into the defects after radical debridement. After approximately eight weeks, the defects were implanted with bone graft.

Results

The patients were followed for 27.5 months (24 to 32). Radiographic bone union occurred at six months for 26 cases (81%) and clinical healing occurred in 29 cases (90%) at ten months. A total of six cases had a second debridement before bone grafting because of recurrence of infection and one patient required a third debridement. No cases of osteomyelitis had recurred at the time of the last follow-up visit.

Conclusion

The induced membrane technique for the treatment of post-traumatic osteomyelitis is a simple, reliable method, with good early results. However, there are many challenges in determining the scope of the debridement, type of limb fixation and source of bone graft to be used.

Cite this article: Dr Z. Xie. Induced membrane technique for the treatment of bone defects due to post-traumatic osteomyelitis. Bone Joint Res 2016;5:101–105. DOI: 10.1302/2046-3758.53.2000487.

Surgical Debridement Is Superior to Sole Antibiotic Therapy in a Novel Murine Posttraumatic Osteomyelitis Model

Introduction

Bone infections after trauma, i.e. posttraumatic osteomyelitis, pose one of the biggest problems of orthopedic surgery. Even after sufficient clinical therapy including vast debridement of infected bone and antibiotic treatment, regeneration of postinfectious bone seems to be restricted. One explanation includes the large sized defects resulting from sufficient debridement. Furthermore, it remains unclear if inflammatory processes after bone infection do affect bone regeneration. For continuing studies in this field, an animal model is needed where bone regeneration after sufficient treatment can be studied in detail.

Methods

For this purpose we created a stable infection in murine tibiae by Staphylococcus aureus inoculation. Thereafter, osteomyelitic bones were debrided thoroughly and animals were subsequently treated with antibiotics. Controls included debrided, non-infected, as well as infected animals exclusively treated with antibiotics. To verify sufficient treatment of infected bone, different assessments detecting S. aureus were utilized: agar plates, histology and RT-qPCR.

Results

All three detection methods revealed massive reduction or eradication of S. aureus within debrided bones 1 and 2 weeks postoperatively, whereas sole antibiotic therapy could not provide sufficient treatment of osteomyelitic bones. Debrided, previously infected bones showed significantly decreased bone formation, compared to debrided, non-infected controls.

Discussion

Thus, the animal model presented herein provides a reliable and fascinating tool to study posttraumatic osteomyelitis for clinical therapies.